As is known, in Italian patents No. 1 172 391 and 1 186 733, and in the published Italian patent application No. 48430A89, molecules of peptidic nature are known, having anti-hypertensive, analgesic and immunomodulating activity, characterized by the sequence of three radicals of specific .alpha.-amino acids.
Said compounds have been shown to work well in the preparation of drugs having the above characteristics. However, their use has been limited to administration by injection, due to the low resistance shown by these compounds to enzymatic hydrolysis.